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1d0b7aaa | 1 | /* $OpenBSD: auth-rhosts.c,v 1.43 2008/06/13 14:18:51 dtucker Exp $ */ |
8efc0c15 | 2 | /* |
5260325f | 3 | * Author: Tatu Ylonen <ylo@cs.hut.fi> |
5260325f | 4 | * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland |
5 | * All rights reserved | |
5260325f | 6 | * Rhosts authentication. This file contains code to check whether to admit |
7 | * the login based on rhosts authentication. This file also processes | |
8 | * /etc/hosts.equiv. | |
6ae2364d | 9 | * |
bcbf86ec | 10 | * As far as I am concerned, the code I have written for this software |
11 | * can be used freely for any purpose. Any derived versions of this | |
12 | * software must be clearly marked as such, and if the derived work is | |
13 | * incompatible with the protocol description in the RFC file, it must be | |
14 | * called by a name other than "ssh" or "Secure Shell". | |
5260325f | 15 | */ |
8efc0c15 | 16 | |
17 | #include "includes.h" | |
4095f623 | 18 | |
19 | #include <sys/types.h> | |
20 | #include <sys/stat.h> | |
c38f5d19 | 21 | |
22 | #ifdef HAVE_NETGROUP_H | |
23 | # include <netgroup.h> | |
24 | #endif | |
b1842393 | 25 | #include <pwd.h> |
cf851879 | 26 | #include <stdio.h> |
00146caa | 27 | #include <string.h> |
31652869 | 28 | #include <stdarg.h> |
632f2669 | 29 | #include <fcntl.h> |
1d0b7aaa | 30 | #include <unistd.h> |
8efc0c15 | 31 | |
32 | #include "packet.h" | |
31652869 | 33 | #include "buffer.h" |
8efc0c15 | 34 | #include "uidswap.h" |
42f11eb2 | 35 | #include "pathnames.h" |
36 | #include "log.h" | |
6fa724bc | 37 | #include "servconf.h" |
42f11eb2 | 38 | #include "canohost.h" |
31652869 | 39 | #include "key.h" |
40 | #include "hostfile.h" | |
5ca51e19 | 41 | #include "auth.h" |
632f2669 | 42 | #include "misc.h" |
8efc0c15 | 43 | |
8002af61 | 44 | /* import */ |
45 | extern ServerOptions options; | |
b3ad3d88 | 46 | extern int use_privsep; |
8002af61 | 47 | |
aa3378df | 48 | /* |
49 | * This function processes an rhosts-style file (.rhosts, .shosts, or | |
50 | * /etc/hosts.equiv). This returns true if authentication can be granted | |
51 | * based on the file, and returns zero otherwise. | |
52 | */ | |
8efc0c15 | 53 | |
396c147e | 54 | static int |
5260325f | 55 | check_rhosts_file(const char *filename, const char *hostname, |
56 | const char *ipaddr, const char *client_user, | |
57 | const char *server_user) | |
8efc0c15 | 58 | { |
5260325f | 59 | FILE *f; |
60 | char buf[1024]; /* Must not be larger than host, user, dummy below. */ | |
632f2669 | 61 | int fd; |
62 | struct stat st; | |
5260325f | 63 | |
64 | /* Open the .rhosts file, deny if unreadable */ | |
632f2669 | 65 | if ((fd = open(filename, O_RDONLY|O_NONBLOCK)) == -1) |
5260325f | 66 | return 0; |
632f2669 | 67 | if (fstat(fd, &st) == -1) { |
68 | close(fd); | |
69 | return 0; | |
70 | } | |
71 | if (!S_ISREG(st.st_mode)) { | |
72 | logit("User %s hosts file %s is not a regular file", | |
73 | server_user, filename); | |
74 | close(fd); | |
75 | return 0; | |
76 | } | |
77 | unset_nonblock(fd); | |
78 | if ((f = fdopen(fd, "r")) == NULL) { | |
79 | close(fd); | |
80 | return 0; | |
81 | } | |
5260325f | 82 | while (fgets(buf, sizeof(buf), f)) { |
83 | /* All three must be at least as big as buf to avoid overflows. */ | |
84 | char hostbuf[1024], userbuf[1024], dummy[1024], *host, *user, *cp; | |
85 | int negated; | |
86 | ||
87 | for (cp = buf; *cp == ' ' || *cp == '\t'; cp++) | |
88 | ; | |
89 | if (*cp == '#' || *cp == '\n' || !*cp) | |
90 | continue; | |
91 | ||
aa3378df | 92 | /* |
93 | * NO_PLUS is supported at least on OSF/1. We skip it (we | |
94 | * don't ever support the plus syntax). | |
95 | */ | |
5260325f | 96 | if (strncmp(cp, "NO_PLUS", 7) == 0) |
97 | continue; | |
98 | ||
aa3378df | 99 | /* |
100 | * This should be safe because each buffer is as big as the | |
101 | * whole string, and thus cannot be overwritten. | |
102 | */ | |
013b1214 | 103 | switch (sscanf(buf, "%1023s %1023s %1023s", hostbuf, userbuf, |
104 | dummy)) { | |
5260325f | 105 | case 0: |
b3ad3d88 | 106 | auth_debug_add("Found empty line in %.100s.", filename); |
5260325f | 107 | continue; |
108 | case 1: | |
109 | /* Host name only. */ | |
110 | strlcpy(userbuf, server_user, sizeof(userbuf)); | |
111 | break; | |
112 | case 2: | |
113 | /* Got both host and user name. */ | |
114 | break; | |
115 | case 3: | |
b3ad3d88 | 116 | auth_debug_add("Found garbage in %.100s.", filename); |
5260325f | 117 | continue; |
118 | default: | |
119 | /* Weird... */ | |
120 | continue; | |
121 | } | |
122 | ||
123 | host = hostbuf; | |
124 | user = userbuf; | |
125 | negated = 0; | |
126 | ||
127 | /* Process negated host names, or positive netgroups. */ | |
128 | if (host[0] == '-') { | |
129 | negated = 1; | |
130 | host++; | |
131 | } else if (host[0] == '+') | |
132 | host++; | |
133 | ||
134 | if (user[0] == '-') { | |
135 | negated = 1; | |
136 | user++; | |
137 | } else if (user[0] == '+') | |
138 | user++; | |
139 | ||
140 | /* Check for empty host/user names (particularly '+'). */ | |
141 | if (!host[0] || !user[0]) { | |
142 | /* We come here if either was '+' or '-'. */ | |
b3ad3d88 | 143 | auth_debug_add("Ignoring wild host/user names in %.100s.", |
144 | filename); | |
5260325f | 145 | continue; |
146 | } | |
147 | /* Verify that host name matches. */ | |
148 | if (host[0] == '@') { | |
149 | if (!innetgr(host + 1, hostname, NULL, NULL) && | |
150 | !innetgr(host + 1, ipaddr, NULL, NULL)) | |
151 | continue; | |
152 | } else if (strcasecmp(host, hostname) && strcmp(host, ipaddr) != 0) | |
153 | continue; /* Different hostname. */ | |
154 | ||
155 | /* Verify that user name matches. */ | |
156 | if (user[0] == '@') { | |
157 | if (!innetgr(user + 1, NULL, client_user, NULL)) | |
158 | continue; | |
159 | } else if (strcmp(user, client_user) != 0) | |
160 | continue; /* Different username. */ | |
161 | ||
162 | /* Found the user and host. */ | |
163 | fclose(f); | |
164 | ||
165 | /* If the entry was negated, deny access. */ | |
166 | if (negated) { | |
b3ad3d88 | 167 | auth_debug_add("Matched negative entry in %.100s.", |
4e2e5cfd | 168 | filename); |
5260325f | 169 | return 0; |
170 | } | |
171 | /* Accept authentication. */ | |
172 | return 1; | |
8efc0c15 | 173 | } |
8efc0c15 | 174 | |
5260325f | 175 | /* Authentication using this file denied. */ |
176 | fclose(f); | |
177 | return 0; | |
8efc0c15 | 178 | } |
179 | ||
aa3378df | 180 | /* |
181 | * Tries to authenticate the user using the .shosts or .rhosts file. Returns | |
182 | * true if authentication succeeds. If ignore_rhosts is true, only | |
183 | * /etc/hosts.equiv will be considered (.rhosts and .shosts are ignored). | |
184 | */ | |
8efc0c15 | 185 | |
6ae2364d | 186 | int |
5260325f | 187 | auth_rhosts(struct passwd *pw, const char *client_user) |
8efc0c15 | 188 | { |
5260325f | 189 | const char *hostname, *ipaddr; |
8002af61 | 190 | |
c5a7d788 | 191 | hostname = get_canonical_hostname(options.use_dns); |
8002af61 | 192 | ipaddr = get_remote_ipaddr(); |
b3ad3d88 | 193 | return auth_rhosts2(pw, client_user, hostname, ipaddr); |
8002af61 | 194 | } |
195 | ||
b3ad3d88 | 196 | static int |
197 | auth_rhosts2_raw(struct passwd *pw, const char *client_user, const char *hostname, | |
8002af61 | 198 | const char *ipaddr) |
199 | { | |
200 | char buf[1024]; | |
5260325f | 201 | struct stat st; |
202 | static const char *rhosts_files[] = {".shosts", ".rhosts", NULL}; | |
1e3b8b07 | 203 | u_int rhosts_file_index; |
5260325f | 204 | |
8002af61 | 205 | debug2("auth_rhosts2: clientuser %s hostname %s ipaddr %s", |
206 | client_user, hostname, ipaddr); | |
207 | ||
5260325f | 208 | /* Switch to the user's uid. */ |
63bd8c36 | 209 | temporarily_use_uid(pw); |
aa3378df | 210 | /* |
211 | * Quick check: if the user has no .shosts or .rhosts files, return | |
212 | * failure immediately without doing costly lookups from name | |
213 | * servers. | |
214 | */ | |
5260325f | 215 | for (rhosts_file_index = 0; rhosts_files[rhosts_file_index]; |
184eed6a | 216 | rhosts_file_index++) { |
5260325f | 217 | /* Check users .rhosts or .shosts. */ |
218 | snprintf(buf, sizeof buf, "%.500s/%.100s", | |
219 | pw->pw_dir, rhosts_files[rhosts_file_index]); | |
220 | if (stat(buf, &st) >= 0) | |
221 | break; | |
8efc0c15 | 222 | } |
5260325f | 223 | /* Switch back to privileged uid. */ |
224 | restore_uid(); | |
225 | ||
226 | /* Deny if The user has no .shosts or .rhosts file and there are no system-wide files. */ | |
227 | if (!rhosts_files[rhosts_file_index] && | |
42f11eb2 | 228 | stat(_PATH_RHOSTS_EQUIV, &st) < 0 && |
229 | stat(_PATH_SSH_HOSTS_EQUIV, &st) < 0) | |
5260325f | 230 | return 0; |
231 | ||
5260325f | 232 | /* If not logging in as superuser, try /etc/hosts.equiv and shosts.equiv. */ |
233 | if (pw->pw_uid != 0) { | |
184eed6a | 234 | if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr, |
235 | client_user, pw->pw_name)) { | |
b3ad3d88 | 236 | auth_debug_add("Accepted for %.100s [%.100s] by /etc/hosts.equiv.", |
184eed6a | 237 | hostname, ipaddr); |
5260325f | 238 | return 1; |
239 | } | |
184eed6a | 240 | if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr, |
241 | client_user, pw->pw_name)) { | |
b3ad3d88 | 242 | auth_debug_add("Accepted for %.100s [%.100s] by %.100s.", |
184eed6a | 243 | hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV); |
5260325f | 244 | return 1; |
245 | } | |
8efc0c15 | 246 | } |
aa3378df | 247 | /* |
248 | * Check that the home directory is owned by root or the user, and is | |
249 | * not group or world writable. | |
250 | */ | |
5260325f | 251 | if (stat(pw->pw_dir, &st) < 0) { |
bbe88b6d | 252 | logit("Rhosts authentication refused for %.100s: " |
b3ad3d88 | 253 | "no home directory %.200s", pw->pw_name, pw->pw_dir); |
254 | auth_debug_add("Rhosts authentication refused for %.100s: " | |
255 | "no home directory %.200s", pw->pw_name, pw->pw_dir); | |
5260325f | 256 | return 0; |
8efc0c15 | 257 | } |
5260325f | 258 | if (options.strict_modes && |
259 | ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || | |
184eed6a | 260 | (st.st_mode & 022) != 0)) { |
bbe88b6d | 261 | logit("Rhosts authentication refused for %.100s: " |
b3ad3d88 | 262 | "bad ownership or modes for home directory.", pw->pw_name); |
263 | auth_debug_add("Rhosts authentication refused for %.100s: " | |
264 | "bad ownership or modes for home directory.", pw->pw_name); | |
5260325f | 265 | return 0; |
8efc0c15 | 266 | } |
5260325f | 267 | /* Temporarily use the user's uid. */ |
63bd8c36 | 268 | temporarily_use_uid(pw); |
5260325f | 269 | |
270 | /* Check all .rhosts files (currently .shosts and .rhosts). */ | |
271 | for (rhosts_file_index = 0; rhosts_files[rhosts_file_index]; | |
184eed6a | 272 | rhosts_file_index++) { |
5260325f | 273 | /* Check users .rhosts or .shosts. */ |
274 | snprintf(buf, sizeof buf, "%.500s/%.100s", | |
275 | pw->pw_dir, rhosts_files[rhosts_file_index]); | |
276 | if (stat(buf, &st) < 0) | |
277 | continue; | |
278 | ||
aa3378df | 279 | /* |
280 | * Make sure that the file is either owned by the user or by | |
281 | * root, and make sure it is not writable by anyone but the | |
282 | * owner. This is to help avoid novices accidentally | |
283 | * allowing access to their account by anyone. | |
284 | */ | |
5260325f | 285 | if (options.strict_modes && |
286 | ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || | |
184eed6a | 287 | (st.st_mode & 022) != 0)) { |
bbe88b6d | 288 | logit("Rhosts authentication refused for %.100s: bad modes for %.200s", |
5260325f | 289 | pw->pw_name, buf); |
b3ad3d88 | 290 | auth_debug_add("Bad file modes for %.200s", buf); |
5260325f | 291 | continue; |
292 | } | |
293 | /* Check if we have been configured to ignore .rhosts and .shosts files. */ | |
294 | if (options.ignore_rhosts) { | |
b3ad3d88 | 295 | auth_debug_add("Server has been configured to ignore %.100s.", |
296 | rhosts_files[rhosts_file_index]); | |
5260325f | 297 | continue; |
298 | } | |
299 | /* Check if authentication is permitted by the file. */ | |
300 | if (check_rhosts_file(buf, hostname, ipaddr, client_user, pw->pw_name)) { | |
b3ad3d88 | 301 | auth_debug_add("Accepted by %.100s.", |
302 | rhosts_files[rhosts_file_index]); | |
5260325f | 303 | /* Restore the privileged uid. */ |
304 | restore_uid(); | |
b3ad3d88 | 305 | auth_debug_add("Accepted host %s ip %s client_user %s server_user %s", |
306 | hostname, ipaddr, client_user, pw->pw_name); | |
5260325f | 307 | return 1; |
308 | } | |
8efc0c15 | 309 | } |
8efc0c15 | 310 | |
5260325f | 311 | /* Restore the privileged uid. */ |
312 | restore_uid(); | |
313 | return 0; | |
8efc0c15 | 314 | } |
b3ad3d88 | 315 | |
316 | int | |
317 | auth_rhosts2(struct passwd *pw, const char *client_user, const char *hostname, | |
318 | const char *ipaddr) | |
319 | { | |
320 | int ret; | |
321 | ||
322 | auth_debug_reset(); | |
323 | ret = auth_rhosts2_raw(pw, client_user, hostname, ipaddr); | |
324 | if (!use_privsep) | |
325 | auth_debug_send(); | |
326 | return ret; | |
327 | } |